Substrate holding method, substrate holding apparatus, exposure apparatus and exposure method

ABSTRACT

A wafer holding apparatus for holding a wafer including a wafer holder on which the wafer is placed; and a lift pin that is configured to be lifted up and down with respect to the wafer holder in a direction along a normal line of a placement surface of the wafer, the lift pin includes a tip part, the tip part includes: a bottom part that forms a suction region for sucking a rear surface of the wafer; and a convex part that supports the rear surface of the wafer in the suction region. When a substrate is placed on a target position, it is possible to prevent a local deterioration of flatness of the substrate even if the substrate is large.

This application is a continuation application of U.S. patentapplication Ser. No. 14/892,336 filed on Jan. 4, 2016, in whichreference is incorporated in its entirety.

TECHNICAL FIELD

The present invention relates to a substrate holding technology thatholds a substrate, an exposure technology using this substrate holdingtechnology and a device manufacturing technology using this exposuretechnology.

BACKGROUND ART

In order to hold a circular semiconductor wafer (hereinafter, it isreferred to as a “wafer” simply) for example as a substrate that is anexposed target, what we call a pin-chuck type of wafer holder in whichthree lift pins (center pins) for example that is capable of beinglifted up and down (going up and down) for carrying a wafer are disposedbetween many pin-shaped small protruding parts is used by an exposureapparatus such as what we call a stepper or a scanning stepper that isused in a photolithography process for manufacturing an electronicdevice (a micro device) such as a semiconductor element. Moreover, aSEMI standards (Semiconductor Equipment and Materials Internationalstandards) for a diameter of the wafer becomes larger at a rate of 1.25times to 1.5 times per every several years to be 125 mm, 150 mm, 200 mmand then 300 mm.

The lift pin that is placed in the conventional wafer holder is abar-shaped component in which a size of its tip part that contacts withthe wafer is approximately same as a size of a lower part below the tippart, and an exhaust hole for vacuum suction using suction force that isgenerated at a negative pressure region is formed at a center portionthereof (for example, refer to a Patent Literature 1).

CITATION LIST Patent Literature

Patent Literature 1: U.S. Pat. No. 6,590,633

SUMMARY OF INVENTION Technical Problem

Recently, the SEMI standards proceeds with a standardization of thewafer having a diameter of 450 mm to improve throughput in manufacturingthe electronic device. If the wafer becomes larger in this manner, theconventional method of simply allowing the bar-shaped three lift pinsfor holding the wafer to lift and carrying the wafer to a placementsurface of the wafer holder (an upper surface of many protrudingportions) may not generate adequate suction force to the wafer and maylead to local deformation (distortion) of the wafer at a position of thelift pin. If the wafer is locally distorted in this manner, residualdistortion or the like of the wafer may lead to a partial gap (a space)between the wafer and the placement surface for the wafer. If there isthe partial gap between the wafer and the placement surface for thewafer in this manner, flatness of an exposed region of the wafer maydeteriorate and exposure accuracy (resolution or the like) may partiallydeteriorate.

An aspect of the present invention considers this condition and itsobject is to suppress the local deterioration of the flatness of asubstrate in placing the substrate that is a held target at a targetposition even if the substrate is large.

Solution to Problem

According to a first aspect of the present invention, there is provideda substrate holding apparatus for holding a substrate, including: asubstrate holding part on which the substrate is placed; and asupporting member that is configured to be lifted up and down withrespect to the substrate holding part, an end part of the supportingmember including: a suction part that forms a suction region for suckinga rear surface of the substrate; and a supporting part that supports therear surface of the substrate in the suction region.

According to a second aspect, there is provided a substrate holdingapparatus for holding a substrate, including: a substrate holding parton which the substrate is placed; and a supporting member that isconfigured to be lifted up and down with respect to the substrateholding part, an end part of the supporting member including: a porousmember that includes a space part and allows a pressure of at least oneportion of the space part to be a negative pressure to suck a rearsurface of the substrate; and a wall part that is formed to surround atleast one portion of the porous member.

According to a third aspect, there is provided a substrate holdingapparatus for holding a substrate, including: a substrate holding parton which the substrate is placed; and a supporting member that isconfigured to be lifted up with respect to the substrate holding part,an end part of the supporting member including: a ring-like firstsupporting part that supports a rear surface of the substrate; and asecond supporting part that supports the rear surface of the substratein a region surrounded by the first supporting part.

According to a fourth aspect, there is provided an exposure apparatusthat projects pattern with exposure light and exposes a substrate withthe exposure light via the pattern, including: the substrate holdingapparatus in the aspect of the present invention for holding thesubstrate that is an exposed target; and a stage that moves with thesubstrate holding apparatus being placed thereon.

According to a fifth aspect, there is provided a substrate holdingmethod that uses the substrate holding apparatus in the aspect of thepresent invention, including: moving the end part of the supportingmember of the substrate holding apparatus to an upside of the substrateholding part; receiving the substrate at the end part of the supportingmember; sucking the substrate by the suction part; lifting down the endpart of the supporting member with respect to the substrate holdingpart; stopping the suction of the substrate by the suction part; anddelivering the wafer from the end part of the supporting member to thesubstrate holding part.

According to a sixth aspect, there is provided an exposure method ofprojecting pattern with exposure light and exposing a substrate with theexposure light via the pattern, including: holding the substrate byusing the substrate holding method in the aspect of the presentinvention; and moving the substrate to an exposure position.

According to a seventh aspect, there is provided a method ofmanufacturing device including: forming a pattern of a photosensitivelayer on a substrate by using the exposure apparatus or the exposuremethod in the aspect of the present invention; and processing thesubstrate on which the pattern is formed.

Advantageous Effects of Invention

According to the aspects of the present invention, since the supportingparts that supports the rear surface of the substrate in the suctionregion, the porous member that sucks the rear surface of the substrateor the second supporting part that supports the rear surface of thesubstrate in the region surrounded by the ring-like first supportingpart is placed at the end part of the supporting member, it is possibleto prevent the local deformation of the wafer when the end part of thesupporting member supports the substrate. Thus, when the substrate as aheld target is placed on a target position, it is possible to prevent alocal deterioration of flatness of the substrate even if the substrateis large.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an outline of a structure of anexposure apparatus EX in a first embodiment.

FIG. 2 is a plan view illustrating a wafer stage in FIG. 1

FIG. 3 is a block diagram illustrating a control system and the like ofthe exposure apparatus in FIG. 1

FIG. 4A is a plan view illustrating a wafer holder apparatus in FIG. 1,and FIG. 4B is a diagram illustrating a cross-sectional view of FIG. 4Athat is observed from the front and a control part.

FIG. 5A is an enlarged plan view illustrating a lift pin of the waferholding apparatus, FIG. 5B is a vertical cross-sectional viewillustrating the lift pin in FIG. 5A from which one portion is omitted,FIG. 5C is an enlarged plan view illustrating a lift pin in the modifiedexample, and FIG. 5D is a vertical cross-sectional view illustrating thelift pin in another modified example from which one portion is omitted.

FIG. 6 is a flow chart illustrating one example of an exposure methodincluding a method of holding the wafer.

FIG. 7A is a cross-sectional view illustrating a state where the waferis carried to the lift pin, and FIG. 7B is a cross-sectional viewillustrating a state where a center part of the wafer contacts with awafer holder.

FIG. 8A is an enlarged cross-sectional view illustrating one portion ofthe wafer that is supported by the lift pin in the embodiment, and FIG.8B is an enlarged cross-sectional view illustrating one portion of thewafer that is supported by the lift pin in the modified example.

FIG. 9 is a plan view illustrating a wafer holding apparatus in themodified example.

FIG. 10A is an enlarged plan view illustrating a lift pin in themodified example, FIG. 10B is a vertical cross-sectional viewillustrating the lift pin in FIG. 10A from which one portion is omitted,FIG. 10C is an enlarged plan view illustrating a lift pin in anothermodified example, FIG. 10D is a vertical cross-sectional viewillustrating the lift pin in FIG. 10C from which one portion is omitted,and FIG. 10E is an enlarged plan view illustrating a lift pin inadditional another modified example.

FIG. 11A is an enlarged plan view illustrating a lift pin in anothermodified example, FIG. 11B is an enlarged plan view illustrating a liftpin in additional another modified example, and FIG. 11C is an enlargedplan view illustrating a lift pin in another modified example.

FIG. 12A is an enlarged plan view illustrating a lift pin in a secondembodiment, and FIG. 12B is a vertical cross-sectional view illustratingthe lift pin in FIG. 11A from which one portion is omitted.

FIG. 13 is a flowchart illustrating one example of a method formanufacturing an electronic device.

DESCRIPTION OF EMBODIMENTS First Embodiment

With reference to FIG. 1 to FIG. 8B, a first embodiment of the presentinvention will be explained. FIG. 1 illustrate an outline of a structureof an exposure apparatus EX that includes a wafer holding apparatus (asubstrate holding apparatus) in the present embodiment. The exposureapparatus EX is a scan-exposure type of projection exposure apparatusthat includes scanning stepper (a scanner). The exposure apparatus EXincludes a projection optical system PL (a projection unit PU).Hereinafter, the embodiment will be explained under the condition wherea Z axis is set to be parallel to an optical axis AX of the projectionoptical system PL, a Y axis is set to be along a direction in which ascanning of a reticle R relative to a wafer (a semiconductor wafer) W isperformed in a surface that is perpendicular to the Z axis, and a X axisis set to be along a direction that is perpendicular to the Z axis andthe Y axis. Moreover, rotational directions around axes that areparallel to the X axis, the Y axis and the Z axis respectively arereferred to as a θX direction, a θY direction and a θZ direction,respectively. In the present embodiment, a plane (a XY plane) that isperpendicular to the Z axis is approximately parallel to a horizontalplane, and −Z direction is a direction of an approximately verticalline.

The exposure apparatus EX includes: an illumination system ILS that isdisclosed in United States Patent Application Publication No.2003/0025890 for example; and a reticle state RST that holds the reticleR (a mask) that is illuminated by illumination light (exposure light) ILfor exposure (for example, ArF excimer laser light having wavelength of193 nm, harmonic wave of solid-state laser (semiconductor laser or thelike) or the like) from the illumination system ILS. Moreover, theexposure apparatus EX includes: the projection unit PU including theprojection optical system PL that exposes the wafer W (a substrate) withthe illumination light IL emitted from the reticle R; a wafer holdingapparatus 8 that holds the wafer W (refer to FIG. 3); a wafer stage WSTthat moves while supporting a mechanical unit of the wafer holdingapparatus 8; and a control system and the like (see FIG. 3).

The reticle R is held on an upper surface of the reticle stage RST byvacuum suction or the like and circuit pattern and the like is formed ona pattern surface (a lower surface) of the reticle R. The reticle stageRST is finely movable in the XY plane on a not-illustrated reticle baseby a reticle stage driving system 25 in FIG. 3 including a linear motoror the like for example, and is movable at a designated scan speed in ascan direction (a Y direction).

Position information (including positions in a X direction and the Ydirection and rotational angle in the θZ direction) of the reticle stageRST in a moving surface is continuously detected by a reticleinterferometer 24 including a reticle interferometer via a movablemirror 22 (or end surface of the stage that is mirror-polished) with aresolution of 0.5 nm to 0.1 nm, for example. The detected value of thereticle interferometer 24 is outputted to a main control apparatus 20including a computer in FIG. 3. The main control apparatus 20 controlsthe reticle stage driving system 25 on the basis of the detected valueand thus controls the position and speed of the reticle stage RST.

In FIG. 1, the projection unit PU that is placed below the reticle stageRST includes: lens barrel 40; and the projection optical system PLhaving a plurality of optical elements that are held to have apredetermined positional relationship in the lens barrel 40. A planarframe (hereinafter, it is referred to as a “measurement frame”) 16 issupported by a not-illustrated frame body via a plurality of vibrationisolating apparatuses (not illustrated), and the projection unit PL isplaced in an opening that is formed at the measurement frame 16 via aflange part FL. The projection optical system PL is a both-sidestelecentric system and has a predetermined projection magnification β(for example, a reduction magnification such as ¼ times, ⅕ times or thelike).

When a illumination region IAR of the reticle R is illuminated with theillumination light IL from the illumination system ILS, the illuminationlight IL that passes through the reticle R generates an image of thecircuit pattern in the illumination region IAR at an exposed region IA(a region that is conjugate to the illumination region IAR) in one shotregion of the wafer W via the projection optical system PL. The wafer Wincludes, as one example, a large circular base material that includesthe semiconductor such as a silicon and has a diameter of 300 mm, 450 mmor the like and on which photoresist (photosensitive material) having athickness of tens of nanometer to 200 nm is coated. A thickness of thebase material having the diameter of 300 mm is 775 μm, for example. Athickness of the base material having the diameter of 450 mm is 900 μmto 1100 μm (for example, about 925 μm) at present, for example.

Moreover, in order to allow the exposure apparatus EX to expose by usingliquid immersion method, a nozzle unit 32 that is one portion of a localliquid immersion apparatus 38 is placed to surround a lower end part ofthe lens barrel 40 holding a front end lens that is the optical elementbeing closest to an image plane (the wafer W) and constituting theprojection optical system PL. The nozzle unit 32 is coupled to a liquidsupply apparatus 34 and a liquid recovery apparatus 36 (refer to FIG. 3)via a supply pipe 31A that is for supplying liquid Lq (for example,purified water) for the exposure and a recovery pipe 31B. Incidentally,if the liquid immersion type of exposure apparatus is not used, theabove described local liquid immersion apparatus 38 may not be provided.

Moreover, the exposure apparatus EX includes: a special imagemeasurement system (not illustrated) that measures a position of animage of an alignment mark (a reticle mark) of the reticle R generatedby the projection optical system PL to align the reticle R; an imageprocessing type (FIA system) of alignment system AL, for example, thatis used to align the wafer W; an oblique incident type of automaticfocusing sensor (hereinafter, it is referred to as a “multipoint AFsystem”) 90 (refer to FIG. 3) for multipoint that includes an lightemitting system 90 a and a light detecting system 90 b and that measuresZ positions of plurality of parts of a front surface of the wafer W; andan encoder 6 (refer to FIG. 3) that is to measure position informationof the wafer stage WST. The special image measurement system is placedin the wafer stage WST, for example.

The alignment system AL includes five alignment systems ALc, ALb, ALa,ALd and ALe that are placed at approximate equal intervals along the Xdirection (non-scan direction) in a region that is placed to be awayfrom the projection optical system PL in −Y direction and whose lengthis about the diameter of the wafer W, as illustrated in FIG. 2 as oneexample. The alignment system AL is configured to simultaneously detectwafer marks at different positions on the wafer W by using fivealignment systems ALa to ALe. Moreover, a loading position LP thatcorresponds to a center position of the wafer stage WST when the wafer Wis loaded and an unloading position UP that corresponds to the centerposition of the wafer stage WST when the wafer W is unloaded arerespectively set at positions that are away from the alignment systemsALa to ALe in −Y direction and that are respectively shifted in −Xdirection and +X direction. A wafer carriage robot WLD (refer to FIG. 1)that loads the wafer W is placed near the loading position LP and awafer carriage robot (not illustrated) that unloads the wafer W isplaced near the unloading position UP.

Moreover, in FIG. 2, the light emitting system 90 a and the lightdetecting system 90 b of the multipoint AF system 90 are placed along aregion that is between the alignment systems ALa to ALe and theprojection optical system PL, for example. According to thisarrangement, the wafer stage WST is driven to move the wafer W in the Ydirection to an exposure start position that is below the projectionoptical system PL after the wafer W is loaded on the wafer stage WST,and thus the multipoint AF system 90 is capable of efficiently measuringa distribution of the Z positions of the front surface of the wafer Wand the alignment systems ALa to ALe is capable of efficiently measuringthe positions of the plurality of wafer marks (mark or the like that isformed in each shot region of the wafer W). A measurement result of themultipoint AF system 90 and a measurement result of the alignment systemAL are outputted to the main control apparatus 20.

In FIG. 1, the wafer stage WST is supported in a non-contact manner byan upper surface WBa that is parallel to a XY surface of a base plate WBvia a plurality of non-illustrated vacuum pre-loadable pneumatic staticpressure bearings (air pads). The wafer stage WST is movable in the Xdirection and the Y direction by a stage driving system 18 (refer toFIG. 3) including a planar motor or two pairs of linear motors that areorthogonal to each other, for example. The wafer stage WST includes: astage body 30 which is moved in the X direction and the Y direction; awafer table WTB that is placed, as a Z stage, on the stage body 30; anda Z stage driving unit that is placed in the stage body 30 and thatfinely adjusts the Z position and tilt angles in the θX direction andthe θY direction of the wafer table WTB relative to the stage body 30. Awafer holder 54 that holds the wafer W by vacuum suction or the like ona placement surface that is approximately parallel to the XY surface isplaced inside an opening placed at a center of the wafer table WTB. Themechanical unit 50 (refer to FIG. 3) of the wafer holding apparatus 8 isconfigured to include the wafer holder 54. Incidentally, the wafer stagebody 30 itself may be configured to move as a six degrees of freedomstage (in X, Y, Z, θX, θY and θZ directions) by the planar motor or thelike.

Moreover, plate-shaped plate body 28 having high flatness is placed onan upper surface of the wafer table WTB, the plate body 28 has a surfacethat is subjected to the liquid-repellent process for the liquid Lq andthat is at the same level as the front surface of the wafer W, an outershape (a contour) of the plate body 28 is rectangular and a circularopening that is larger than a placement region for the wafer W is formedat a center position of the plate body 28.

Incidentally, in what we call the liquid immersion type of exposureapparatus including the above described local liquid immersion apparatus38, as illustrated in a plane view of the wafer stage WST in FIG. 2, theplate body 28 further includes: a plate part (liquid repellent plate) 28b that surrounds the circular opening 28 a, that has a rectangular outershape and that has a surface being subjected to the liquid-repellentprocess; and a periphery part 28 c that surrounds the plate part 28 b.One pair of two-dimensional diffraction gratings 12A and 12B and onepair of two-dimensional diffraction gratings 12C and 12D are placed onan upper surface of the periphery part 28 c. The pair of two-dimensionaldiffraction gratings 12A and 12B is elongated in the X direction tosandwich the plate part 28 b in the Y axis direction. The pair oftwo-dimensional diffraction gratings 12C and 12D is elongated in the Ydirection to sandwich the plate part 28 b in the X axis direction. Eachof the diffraction gratings 12A to 12D is a reflective type ofdiffraction grating having a two-dimensional grating pattern whoseperiodical direction is the X direction and the Y direction and whosecycle is about 1 μm.

In FIG. 1, a plurality of three-axis detection heads 14 that irradiatethe diffraction gratings 12C and 12D with laser light (measurementlight) for the measurement and that measure a relative(three-dimensional) position relative to the diffraction grating in theX direction, the Y direction and the Z direction are placed on a bottomsurface of the measurement frame 16 to sandwich the projection opticalsystem PL in the X direction (refer to FIG. 2). Moreover, a plurality ofthree-axis detection heads 14 that irradiate the diffraction gratings12A and 12B with the laser light for the measurement and that measurethe relative three-dimensional position relative to the diffractiongrating are placed on the bottom surface of the measurement frame 16 tosandwich the projection optical system PL in the Y direction (refer toFIG. 2). Moreover, there are also provided one laser source or aplurality of laser sources (not illustrated) for supplying the laserlight (the measurement light and reference light) to the plurality ofdetection heads 14.

In FIG. 2, during a period during which the wafer W is exposed via theprojection optical system PL, two detection heads 14 in a row A1 in theY direction irradiate the diffraction grating 12A or 12B with themeasurement light and supplies to a respective one measurementprocessing unit 42 (refer to FIG. 3) detection signal of interferinglight generated by interference between the reference light anddiffracted light generated from the diffraction gratings 12A and 12B. Inparallel to this, two detection heads 14 in a row A2 in the X directionirradiate the diffraction grating 12C or 12D with the measurement lightand supplies to a respective one measurement processing unit 42 (referto FIG. 3) detection signal of interfering light generated byinterference between the reference light and diffracted light generatedfrom the diffraction gratings 12C and 12D. These measurement processingunits 42 for the detection heads 14 in the row A1 and the row A2calculate the relative positions (relative movement amounts) in the Xdirection, the Y direction and the Z direction of the wafer stage WST(the wafer W) relative to the measurement frame 16 (the projectionoptical system PL) at a resolution of 0.5 nm to 0.1 nm for example, andsupply the calculated value to a switching unit 80A and a switching unit80B. The switching units 80A and 80B for the calculated value supply tothe main control apparatus 20 information of the relative positions thatare supplied from the measurement processing units 42 corresponding tothe detection heads 14 that face the diffraction gratings 12A to 12D.

The three-axis encoder 6 is constructed of the plurality of detectionheads 14 in the row A1 and the row A2, the laser source (notillustrated), the plurality of measurement processing units 42, theswitching units 80A and 80B and the diffraction gratings 12A to 12D. Adetailed structure of each of this encoder and five alignment systemsare disclosed in United States Patent Application Publication No.2008/094593, for example. The main control apparatus 20 obtainsinformation relating to positions in the X direction, the Y directionand the Z direction and the rotational angle in the θZ direction and thelike of the wafer stage WST (the wafer W) relative to the measurementframe 16 (the projection optical system PL) on the basis of informationof the relative positions that are supplied from the encoder 6 and movesthe wafer stage WST on the basis of this information by using the stagedriving system 18.

Incidentally, a laser interferometer that measures the three-dimensionalposition of the wafer stage WST may be provided in addition to orinstead of the encoder 6 and the wafer stage WST may be moved by usingthe measurement value of the laser interferometer.

When the exposure apparatus EX performs the exposure, the reticle R andthe wafer W are aligned firstly as a basic operation. Then, the image ofthe pattern of the reticle R is transferred onto one shot region bystarting to illuminate the reticle R with the illumination light IL andperforming a scanning exposure operation that projects the image of oneportion of the pattern of the reticle R on one shot region on the frontsurface of the wafer W via the projection optical system whilesynchronously moving (synchronously scanning) the reticle stage RST andthe wafer stage WST in the Y direction with the projection magnitude βof the projection optical system PL being set as a speed ratio. Then, anoperation (a step movement operation) that moves the wafer W in the Xdirection and the Y direction via the wafer stage WST and the abovedescribed scanning exposure operation are repeated and thus the image ofthe pattern is transferred onto all shot regions of the wafer W by astep-and-scan method and the liquid immersion method.

At this time, optical path lengths of the measurement light and thediffracted light in each detection head 14 of the encoder 6 are shorterthan that of the laser interferometer. Thus, the image of the pattern ofthe reticle R can be transferred onto the wafer W highly precisely.Incidentally, in the present embodiment, the detection heads 14 areplaced at a side of the measurement frame 16 and the diffractiongratings 12A to 12D are placed at a side of the wafer stage WST. Asanother structure, the diffraction gratings 12A to 12D may be placed atthe side of the measurement frame 16 and the detection heads 14 may beplaced at the side of the wafer stage WST

Next, the structure and the operation of the wafer holding apparatus 8in the present embodiment will be explained in detail. The wafer holdingapparatus 8 includes: the mechanical unit 50 including the wafer holder54 that is placed in the wafer stage WST; and a wafer holder controlsystem 51 that controls an operation of the mechanical unit 50 under thecontrol of the main control apparatus 20.

FIG. 4A is a plan view illustrating the wafer holder apparatus 8 inFIG. 1. FIG. 4B illustrates a vertical cross-sectional view (across-sectional view that is observed from the front) of a centerportion of FIG. 4A in the X direction and the wafer holder controlsystem 51. In FIG. 4B, the Z stage 53 that is made of a metal having alow expansion rate, for example, is supported on an upper surface of thestage body 30 via driving units (not illustrated) at three positionseach of which uses a voice coil motor method, for example, and allowsthe movement in Z direction. The Z stage 53 corresponds to the wafertable WTB in FIG. 1.

The Z stage 53 is a rectangular box-shaped member whose upper part isopened. The wafer holder 54 is fixed at an inner surface 53 a that isapproximately parallel to the XY plane and is in a concaved part atcenter of the Z stage 53. The wafer W is held by the wafer holder 54.The diffraction gratings 12A to 12D are fixed at an upper surface of aside wall part of the Z stage 53 via the plate body 28.

Moreover, a bottom part of the wafer holder 54 has a circular and planarplate-like shape. A side wall part 54 c that has a closed ring-likeshape is integrally formed on an upper surface of the bottom part. Asize of the side wall part 54 c is slightly smaller than an edge part ofa periphery of the wafer W that is a held target. The side wall part 54c supports a periphery part of the wafer W. If the diameter of the waferW is 300 mm or 450 mm, the side wall part 54 c is formed so that itsouter diameter is slightly smaller than 300 mm or 450 mm. The waferholder 54 is made of a material having a very low thermal expansionrate, for example, as one example. A super low expansion glass (forexample, ULE (a trade name) of Corning company), a glass-ceramic havinga super low expansion rate (for example, Zerodur (a trade name) ofSchott company), a silicon carbide (SiC) or the like can be used as thismaterial.

Moreover, as illustrated in FIG. 4A, a plurality of pin-shapedprotruding parts 54 b are integrally formed at positions correspondingto grid points of two-dimensional grid having an equilateral-triangularshape as a basic shape, for example, in a region that is surrounded bythe side wall part 54 c on the bottom part of the wafer holder 54. Adistance between plural adjacent protruding parts 54 b is several mm(for example, about 3 mm), for example. Upper surfaces of the pluralityof protruding parts 54 b and the side wall part 54 c are processed tohave an extremely high flatness to contact with same plane(approximately, the XY plane). A surface including the upper surfaces ofthe plurality of protruding parts 54 b and the side wall part 54 ccorresponds to the placement surface 54 a for the wafer W. The wafer Wthat is the exposed target is placed on the placement surface 54 a sothat a gap between a rear surface of the wafer W and the upper surfacesof the plurality of protruding parts 54 b and the side wall part 54 c isnot generated as much as possible. The wafer holder 54 can bemanufactured by performing an integral molding and then a polishing andthe like of front surfaces of the protruding parts 54 b and the like,for example. Incidentally, for the simple illustration, FIG. 4Aillustrates the wafer W by two-dot chain line.

Moreover, a suction hole 55A is formed at an approximate center of aregion that is surrounded by the side wall part 54 c on an upper surfaceof the wafer holder 54. A plurality of first surrounding suction holes55B are formed at approximate equal angle intervals along a firstcircumference C1 that surrounds the suction hole 55A. A plurality ofsecond surrounding suction holes 55C are formed at approximate equalangle intervals along a second circumference C2 that surrounds thesuction hole 55A at the center and that is larger than the firstcircumference C1. A plurality of third surrounding suction holes 55D areformed at approximate equal angle intervals along a third circumferenceC3 that surrounds the suction hole 55A at the center and that is largerthan the second circumference C2. The suction holes 55A to 55D areformed in a region between the plurality of protruding parts 54 b.Incidentally, the suction holes 55A at the center or at the vicinity ofthe center may not be necessarily formed.

In the present embodiment, the number of each of the first to thirdsurrounding suction holes 55B to 55D is preferably larger than six, inorder to suck the rear surface of the wafer W at the placement surface54 a more uniformly and stably. However, the number of each of the firstto third surrounding suction holes 55B to 55D may be any number. Thenumbers of the first to third surrounding suction holes 55B to 55D maybe different from one another. As illustrated in FIG. 4B, the suctionholes 55A, 55B, 55C and 55D communicate with exhaust pipes 61B1, 61B2,61B3 and 61B4 that are placed inside the stage body 30 via exhaustpassages a1 and a2 and the like that are independent from one anotherand that are inside the bottom part of the wafer holder 54 and exhaustpassages a11, a21, a31 and a41 that are independent from one another andthat are inside the Z stage 53, respectively. The exhaust pipes 61B1 to61B4 are coupled to a vacuum pump 62 that is outside the wafer stage WSTvia an exhaust pipe 61A having flexibility.

Valves (hereinafter, each is referred to as a “suction valve”) V11, V12,V13 and V14 that are to start the vacuum suction and valves(hereinafter, each is referred to as a “suction stop valve”) V21, V22,V23 and V24 that are to allow the insides of the exhaust pipes 61B1 to61B4 to communicate with air to stop the vacuum suction are attached tothe exhaust pipes 61B1, 61B2, 61B3 and 61B4, respectively. The waferholder control system 51 controls the opening and the closing of each ofthe valves V11 to V14 and the valves V21 to V24. The bottom part of thewafer holder 54 at which the plurality of suction holes 55A to 55D areformed, the exhaust pipes 61A and 61B1 to 61B4 and the vacuum pump 62constitute a suction unit (a second suction part) for the wafer holder54 that holds the wafer W at the placement surface 54 a of the waferholder 54 by the vacuum suction. This suction unit is one portion ofentire suction unit 52. In the present embodiment, the wafer holdercontrol system 51 is capable of controlling timings for the vacuumsuction of the wafer W and for the stop of the vacuum suction via thesuction holes 55A to 55D independently of one another. Incidentally, thevacuum suction of the wafer W and the stop of the vacuum suction via thesuction holes 55A to 55D may be synchronously performed at the sametiming.

Moreover, a plurality of members (hereinafter, each is referred to as a“lift pin”) each of which elongates in the Z direction and can be liftedup and down (go up and down) in the Z direction while holding the waferW by the vacuum suction are placed at approximate equal angle intervalsalong a circumference CT between the first circumference C1 and thesecond circumference C2 in the region of the wafer holder 54 that issurrounded by the side wall part 54 c, for example. Incidentally, thelift pin 44 are placed near the center of the wafer holder 54 and thusthe lift pin 44 can be referred to as a center pin or an up-and-downpin. At least three lift pins 44 are preferably placed to stably supportthe wafer W. However, the number of the lift pins 44 is not limited tothis number. The number of the lift pins 44 may be larger or smallerthan three, for example. Moreover, the number of the lift pins 44 may bean integral multiple of three such as six or nine, for example. In thepresent embodiment, three lift pins 44 are placed at a positions P1, P2and P3 that are arranged at approximate equal angle intervals along thecircumference CT, respectively. FIG. 4B illustrates the lift pins 44 inthe positions P1 and P3.

If the diameter of the wafer W is 450 mm, a diameter of thecircumference CT along which the plurality of lift pins 44 are placed ispreferably 180 mm to 350 mm (⅖ times to 7/9 times of the diameter of thewafer W), for example, to stably support the wafer W by the plurality oflift pins 44. If the diameter of the wafer W is 450 mm, the diameter ofthe circumference CT may be set about 200 mm, for example.

Moreover, the diameter of the circumference CT along which the lift pins44 are placed may be set so that deflection amount of the wafer W isminimized when the plurality of lift pins 44 support the wafer W,namely, so that the wafer W is supported at positions that correspond towhat we call Bessel points. The diameter of the circumference CTrepresenting the positions that correspond to the Bessel points in thecase where the diameter of the wafer W is 450 mm is about 280 mm to 310mm.

The lift pin 44 includes: an axis part 45 that has an elongated andcylindrical (bar-like) external appearance and that is inserted in anopening formed in the wafer holder 54 and the Z stage 53; and a tip part46 that is coupled to an upper end of the axis part 45 and that facesthe wafer W as the held target to support the wafer W, for example. Asuction hole (passage) 45 a is formed in a center of the axis part 45.The suction hole 45 a includes a circular through hole for forming anegative pressure space that causes suction force (attracting force) invacuum-sucking the wafer W. An outer shape of the tip part 46 is acircular dish-like shape having a diameter that is larger than adiameter of the axis part 45, for example, and a center part of the tippart 46 communicates with the suction hole 45 a. A circular cut part (acounter boring part) 54 d (refer to FIG. 7A) having a size and depththat allows the tip part 46 to be in it is formed at a position that ison the surface of the wafer holder 54 at which the plurality ofprotruding part 54 b are formed and that has the opening through whichthe axis part 45 of the lift pin 44 passes. When the wafer W is placedon the placement surface 54 a of the wafer holder 54 on the plurality ofprotruding part 54 b and the wafer W is exposed, the axis parts 45 ofthe plurality of lift pins 44 are down toward −Z direction and oneportion of the tip part 46 is in the cut part 54 d of the wafer holder54 (in a position that is below the protruding parts 54 d in the Zdirection). Thus, even if a size (thickness) of the tip part 46 in the Zdirection is larger than a size (a thickness) of the protruding part 54b in the Z direction, the tip part 46 is capable of certainly moving toa position (cut part 54 d) that is away from the wafer W. However, ifthe size of the tip part 46 in the Z direction is smaller than the size(the thickness) of the protruding part 54 b in the Z direction, the cutpart 54 b may not be necessarily formed.

Moreover, in FIG. 4B, each of the suction holes 45 a in the axis parts45 of the plurality of lift pins 44 communicates with an exhaust pipe61A having flexibility via an exhaust pipe 60 having flexibility in thestage body 30 and a fixed exhaust pipe 61C. The exhaust pipe 61Acommunicates with the vacuum pump 62. The suction hole of the lift pin44 at the position P2 in FIG. 4A also communicates with the exhaust pipe61C. A suction valve V3 that is to start the vacuum suction by the liftpins 44 and a suction stop valve V4 that is to stop the vacuum suctionare attached to the exhaust pipe 61C. The wafer holder control system 51controls the opening and the closing of each of the valves V3 and V4.The exhaust pipes 60 and 61C, the valves V3 and V4 and the vacuum pump62 constitute a suction unit (a first suction part) that holds the waferW at the tip parts 46 of the plurality of lift pins 44 by the vacuumsuction. This suction unit is one portion of entire suction unit 52.Incidentally, a plurality of vacuum pumps may be provided and the firstand second suction units may be coupled to the vacuum pumps,respectively and independently from each other. In the presentembodiment, the first to third surrounding suction holes 55B to 55D areplaced at positions having approximate same angle in the circumferentialdirection. The plurality of lift pins 44 are placed along thecircumferential direction between the plurality of suction holes 55B and55C.

Moreover, the axis part 45 and the tip part 46 of the lift pin 44 areintegrally formed as one example, however, the axis part 45 and the tippart 46 may be coupled to each other by bond or the like after the axispart 45 and the tip part 46 are formed separately. The lift pin 44 canbe formed of the material having a very low thermal expansion rate suchas the silicon carbide (SiC), a ceramic made of the silicon carbide, thesuper low expansion glass or the glass-ceramic having a super lowexpansion rate, for example, as with the wafer holder 54.

As illustrated in FIG. 4B, each of the axis parts 45 of the plurality oflift pins 44 is lifted up and down (goes up and down) with respect tothe wafer holder 54 in the Z direction by a driving unit 56 that isplaced at a side of a bottom surface of the Z stage 53. A drivingmechanism using a voice coil motor method, a rack and pinion method orthe like can be used as the driving unit 56. Moreover, position sensors57 such as optical linear encoders or the like, for example, are placed.The position sensors 57 measure positions of the axis parts 45 of theplurality of lift pins 44 in the Z direction separately. The measuredvalues by the position sensors 57 for the plurality of lift pins 44 aresupplied to the wafer holder control system 51. The wafer holder controlsystem 51 separately controls each of the positions of the plurality oflift pins 44 in the Z direction via respective one driving unit 56 onthe basis of the measurement result of the plurality of position sensors57.

Moreover, if the tip part 46 of the lift pin 44 contacts with the rearsurface of the wafer W when the lift pin 44 is being lifted up, drivingforce of corresponding one driving unit 56 increases and driving currentincreases, for example. Thus, the wafer holder control system 51monitors the driving currents of the driving units 56 and thus iscapable of determining whether the lift pin 44 contacts with the wafer Won the basis of the variation of the driving currents, for example.Incidentally, the plurality of lift pins 44 are synchronously moved inthe Z direction to be at the same height, however, the plurality of liftpins may be lifted up and down by one driving unit, for example. Thewafer holder 54, the plurality of lift pins 44, the driving units 56 forthese and the suction unit 52 constitute the mechanical unit 50 (referto FIG. 3) of the wafer holding apparatus 8.

Next, with reference to FIG. 5A to FIG. 5D, the lift pin 44 of the waferholding apparatus 8 in the present embodiment will be explained indetail. In the below explanation relating to the lift pin 44, thediameter of the wafer W that is the held target is regarded as 450 mm.

FIG. 5A is an enlarged plan view illustrating the lift pin 44 in FIG.4B. FIG. 5B is a vertical cross-sectional view illustrating the lift pin44 in FIG. 5A from which one portion of the axis part 45 is omitted.

As illustrated in FIG. 5A and FIG. 5B, the tip part 46 that is placed atthe upper end of the axis part 45 of the lift pin 44 includes: acircular-disk-shaped bottom part 46 a having an opening (this is alsoreferred to as the “suction hole 45 a”) communicating with the suctionhole 45 a in the axis part 45; a convex and circular wall part 46 b thatis placed at a periphery of the bottom part 46 a; and a plurality ofconvex parts 46 c that are formed in a suction region 46 s on an uppersurface of the bottom part 46 a surrounded by the wall part 46 b andthat are formed in a region outside the suction hole 45 a. The pluralityof convex parts 46 c have truncated conical shapes that are same as eachother, for example. Thus, even if the convex parts 46 c repeatedlycontact with the wafer, the convex parts 46 c do not deform. Moreover,as illustrated in FIG. 5A, the plurality of convex parts 46 c arearranged along a first circumference and a second circumference whosecenters correspond to the circular suction hole 45 a. Incidentally, theplurality of convex parts 46 c may be formed along one circumferencethat surrounds the suction hole 45 a, and moreover, may be formed alongthree or more circumferences that surround the suction hole 45 a.

Moreover, upper surfaces of the plurality of convex parts 46 c and anupper surface of the wall part 46 b at the tip part 46 are processed tohave high flatness to contact with same plane (virtual plane) Q1.

For example, an outer shape of the wall part 46 b of the tip part 46 ispreferably a circular shape having a diameter φ3 (refer to FIG. 5A) of 5mm to 15 mm and width (thickness) t1 (refer to FIG. 5B of the wall part46 b is preferably 0.05 mm to 0.6 mm. Moreover, the diameter φ3 of theouter shape of the wall part 46 b is more preferably 6 mm to 9 mm. Inthis case, a shape of a tip of each of the plurality of convex parts 46c is preferably a circular shape having a diameter φ4 (refer to FIG. 5B)of 0.05 mm to 0.6 mm. Moreover, height hi (refer to FIG. 5B of each ofthe wall part 46 b and the convex parts 46 c is preferably 20 μm to 500μm.

Moreover, a cross-sectional area of the axis part 45 is set to besmaller than a cross-sectional area of the outer shape of the wall part46 b of the tip part 46. If the shape of the wall part 46 b is thecircular shape having the diameter φ3 of 5 mm to 15 mm, an outer shapeof the axis part 45 is a circular shape having a diameter φ2 (refer toFIG. 5B) of 3 mm to 5 mm and a shape of the suction hole 45 a is acircular shape having a diameter φ1 (refer to FIG. 5B) of 1 mm to 2 mm.For example, if the diameter of the outer shape of the wall part 46 b isabout 8 mm, the diameter of the outer shape of the axis part 45 may beabout 5 mm. Incidentally, the outer shape of the axis part 45 may be apolygonal shape or the like having a cross-sectional area that is closeto that of the circle having the diameter φ2. Similarly, the outer shapeof the wall part 46 b may be also a polygonal shape or the like having across-sectional area that is close to that of the circle having thediameter φ3. The lift pin 44 having this tip part 46 can be manufacturedby molding a material and then polishing the upper surfaces of the wallpart 46 b and the convex parts 46 c, for example. Moreover, the wallpart 46 b and the convex parts 46 c at the tip part 46 of the lift pin44 may be formed by etching or CVD.

Moreover, in the present embodiment, since the rear surface of the waferW is sucked and supported by the lift pins 44, a part (a front surface)of the tip part 46 of each lift pin 44 that contacts with the wafer W ispreferably slippery in order to prevent a local deformation such aswarp, curve or the like of the wafer W supported by the lift pins 44.For this purpose, the front surface of the tip part 46 of each lift pin44 is subjected to a process for reducing friction. The process on thefront surface for reducing the friction includes, as one example, aforming of a DLC (Diamond Like Carbon) film.

Incidentally, the arrangement of the plurality of convex parts 46 c atthe tip part 46 is not limited to the arrangement along thecircumference. As illustrated by the lift pins 44 in FIG. 5C, the convexparts 46 may be placed at grid points of two-dimensional grid having anequilateral-triangular shape (a square shape may be used) as a basicshape, for example, respectively. The plurality of convex parts 46 c maybe placed randomly.

Moreover, as illustrated by convex parts 46 d of the lift pin 44B inFIG. 5D, the shape of each of the plurality of convex parts of the liftpin that contact with the wafer W may be a truncated conical shapehaving two (three or more) steps. The height of this convex part 46 d ispreferably 50 μm to 500 μm, for example. Moreover, the convex part 46 cmay not be solid and may has a tube-like shape (alternatively, pipe-likeshape), for example. In this case, an upper end of the convex part has aring-like shape surrounding the opening, for example, and thering-like-shaped part contacts with the rear surface of the wafer.Moreover, an inside of the tube (the pipe) may be allowed to communicatewith the opening at the bottom part as a passage and thus the wafer maybe sucked by the tip of the convex part 46 c.

Moreover, as illustrated by the lift pin 44B in FIG. 5D, the height ofthe wall part 46 b at the tip part 46 may be lower by gap δ than theheight of the convex part 46 d (a height of plane Q1). The gap δ is 50nm to several micrometer, for example. If the height of the wall part 46b is lower than the height of the convex part 46 d, air flows through agap between the wall part 46 b and the wafer W when the suction hole 45a sucks the air and thus the wafer W can be stably sucked by Bernoullieffect in some cases. Moreover, the height of not entire circumferenceof the wall part 46 b but one portion thereof may be lower than theheight of the convex part 46 d (the height of the plane Q1).

Next, with reference to a flowchart in FIG. 6, one example of a holdingmethod of holding the wafer by using the wafer holding apparatus 8 andan exposure method using this holding method in the exposure apparatusEX in the present embodiment will be explained. The operation in thismethod is controlled by the main control apparatus 20 and the waferholder control system 51. Firstly, the reticle R is loaded on thereticle stage RST in FIG. 1 and the reticle R is aligned at step 102 inFIG. 6. Then, the wafer stage WST moves to the loading position LP inFIG. 2 under the condition where the wafer W is not loaded, and thewafer carriage robot WLD (a wafer loading system) in FIG. 1 carries thenon-exposed and resist-coated wafer W on the wafer stage WST (step 104).At this time, the wafer W that is placed at a folk type of wafer arm(not illustrated) at a tip part of the wafer carriage robot WLD movesabove the wafer holder 54 that is fixed to the wafer stage WST. At thisstate, the suction unit 52 of the wafer holding apparatus 8 stops thesuction (including the suction by the lift pins 44) and the tip parts 46of the lift pins 44 are located below the wafer W.

Then, as illustrated in FIG. 7A, the wafer holder control system 51starts the vacuum suction operation by the suction holes 45 a whilesynchronously lifting up (moving toward +Z direction) all lift pins 44.After tips (the upper surface of the tip part 46) of the lift pins 44contact with the rear surface of the wafer W, the lift pins 44 areslightly lifted up and then stop (step 106). At this time, the wafer Wis sucked by the tips of the lift pins 44 and the position of the waferW relative to the lift pins 44 does not change. At this time, the waferW is carried from the wafer arm to the lift pins 44. Under thiscondition, the wafer arm moves toward −Y direction (step 110).

Then, all lift pins 44 are synchronously lifted down at same speed underthe condition where the wafer W is supported (step 112). Then, asillustrated in FIG. 7B, the suction unit 52 starts the vacuum suctionvia the suction holes 55A to 55D of the wafer holder 54 when the tips(the upper surfaces of the tip parts 46) of the lift pins 44 are closeto the placement surface 54 a, and the suction of the wafer W by thelift pins 44 stops when the tips of the lift pins 44 reach the placementsurface 54 a (step 114). The lift pins 44 stop at a position at whichthe tip parts 46 are below the placement surface 54 a (at which the tipparts 46 are in the cut parts 54 d). Then, as illustrated in FIG. 5B,the rear surface of the wafer W is placed on the placement surface 54 aof the wafer holder 54 and the wafer W is carried from the lift pins 44to the wafer holder 54 (step 116).

At this time, the suction of the wafer by the suction hole 55A at thecenter of the wafer holder 54 may be performed and then the suction ofthe wafer by the surrounding suction holes 55B, 55C and 55D may besequentially performed to gradually expand an area at which the suctionis performed. For this operation, even if the wafer W is large substrate(450 mm wafer) such as a circular-disk-shaped substrate having thediameter of 450 mm, for example, the wafer W does not deform, warp,curve or the like in a wrinkle-like manner easily and the gap is notgenerated partially between the rear surface of the wafer W and theplacement surface 54 a (the upper surfaces of the wall part 54 c and theplurality of protruding parts 54 b), and thus the wafer W is held by thewafer holder 54 to have high flatness.

Moreover, in the present embodiment, as illustrated in FIG. 8A, theplurality of convex parts 46 c are placed to surround the suction hole45 a in the region (the suction region) surrounded by the wall part 46 bat the tip part 46 of each lift pin 44. Thus, the large wafer W can besupported more stably by enlarging the outer shape of the wall part 46b, and the suction force (the attracting force) can be increased byenlarging an area size of the negative region and thus the large wafer Wcan be held by larger suction force stably. Moreover, even when thepressure in the suction region becomes negative by the suction (thevacuum suction), it is possible to prevent the wafer W to locally deformbecause the convex parts 46 c in the suction region support the rearsurface of the wafer W. Thus, the residual distortion of the wafer Wdecreases more when the wafer W is carried from the lift pins 44 to thewafer holder 54.

On the other hand, as illustrated by a lift pin 74 in a comparisonexample in FIG. 8B, if the convex part is not placed inside a wall part46Hb placed at a periphery of a bottom part 46Ha of a tip part 46H, thevacuum suction possibly causes the local distortion of the wafer W andthis distortion may lead to the residual distortion when the wafer W iscarried to the wafer holder 54.

Then, the wafer W is aligned by the alignment system AL during a periodduring which the wafer stage WST moves to allow the wafer W to move toan underside of the projection optical system PL (an exposing position)(step 118). The image of the pattern of the reticle R scanning-exposeseach shot region on the wafer W by moving the wafer W on the basis ofthe result of the alignment (step 120). Then, the wafer stage WST movesto the unloading position UP, the suction unit 52 of the wafer holdingapparatus 8 stops sucking the wafer W, the wafer W is lifted up by thelift pins 44, and the wafer W is carried to the wafer carriage robot(not illustrated) for the unload, and thus the wafer W is unloaded (step122). The unloaded wafer W is carried to a coater/developer (notillustrated) and then is developed. Then, if next wafer is exposed (step124), the operation from the step 104 to the step S122 is repeated.

As described above, according to the exposure method in the presentembodiment, since the outer shape of the tip part 46 of the lift pin 44is large, the wafer W can be supported in a state where the wafer W isstably sucked and supported, even when the wafer W is large. Moreover,since the plurality of convex parts 46 c are placed in the region (thesuction region) surrounded by the wall part 46 b at the tip part 46 ofthe lift pin 44 and the local deformation of the wafer W is preventedwhen the lift pins 44 suck and support the wafer W, the high flatness ofthe wafer W can be maintained when the wafer W is carried to the waferholder 54. Therefore, high throughput can be achieved by using the largewafer W and the image of the pattern of the reticle R can be transferredhighly precisely by maintaining high exposure accuracy (resolution orthe like) at all surface of the wafer W.

As described above, the exposure apparatus EX in the present embodimentincludes the wafer holding apparatus 8 that holds the wafer W (thesubstrate). The wafer holding apparatus 8 includes: the wafer holder 54(a substrate holding part) on which wafer W is placed; and the lift pin44 (a supporting member) that is configured to be lifted up and downwith respect to the wafer holder 54, the tip part 46 (an end part) ofthe lift pin 44 includes: the bottom part 46 a (a suction part) thatforms the suction region 46 s for sucking the rear surface of the waferW; and the convex part 46 c (a supporting part) that supports the rearsurface of the wafer W in the suction region 46 s.

Moreover, from another point of view, the wafer holding apparatus 8includes: the wafer holder 54 (a substrate holding part) on which waferW is placed; and the lift pin 44 (a supporting member) that isconfigured to be lifted up and down with respect to the wafer holder 54,the tip part 46 (an end part) of the lift pin 44 includes: the wall part46 b (a first supporting part) that supports the rear surface of thewafer W and that is ring-like; and the concave part 46 c (a secondsupporting part) that supports the rear surface of the wafer W in thesuction region (a region) surrounded by the wall part 46 b.

Moreover, the method of holding the wafer W by the wafer holdingapparatus 8 includes: the step 106 in which the tip portions 46 (the endparts) of the lift pins 44 contact the wafer W and the lift pins 44 suckthe wafer W; the step 112 at which the tip portions 46 of the lift pins44 are lifted down in the Z direction to a side of the wafer holder 54;and the step 114 at which the suction unit 52 stops sucking the wafer Wvia the lift pins 44.

According to the present embodiment, the convex part 46 c (thesupporting part or the second supporting part) is in the suction region46 s that is surrounded by the wall part 46 b of the tip part 46 whenthe tip part 46 (the end part) of the lift pin 44 supports the wafer Wby the suction for example, and thus the local deformation of the waferW at the tip part 46 can be prevented. Therefore, even if the wafer W islarge, it is possible to stably support the wafer W by enlarging the tippart 46 of the lift pin 44 and it is possible to suppress the localdeterioration of the flatness of the wafer W when the wafer W is placedat the wafer holder 54 (a target position).

Moreover, in the present embodiment, the lift pin 44 is movable in the Zdirection (in a direction along a normal line of the placement surface54 a) through the placement surface 54 a for the wafer W of the waferholder 54, and the lift pin 44 includes: the axis part 45 (a bar-shapedpart) in which the suction hole 45 a (it is also referred to as a firstopening or passage) through which exhausts the air by a first suctionpart is formed; and the tip part 46 that is placed at a tip part of theaxis part 45 to support the wafer W, and the tip part 46 includes: thebottom part 46 a that is configured to face the wafer W via apredetermined gap; the convex wall part 46 b that is placed at thebutton part 46 a so as to surround at least one portion of a surface ofthe button part 46 a that is configured to face the wafer W; and theplurality of convex parts 46 c that are placed at a region of the bottompart 46 a surrounded by the wall part 46 b and that is configured tosupport the wafer W, a region that is surrounded by the bottom part 46 aand the wall part 46 b communicates with the suction hole (the passage)45 a of the axis part 45. Thus, the tip part of the lift pin 44 iscapable of stably holding the rear surface of the wafer W by the vacuumsuction.

Moreover, the exposure apparatus EX in the present embodiment is anexposure apparatus that projects the pattern of the reticle R with theillumination light IL (exposure light) for the exposure and exposes thewafer W with the illumination light IL via the pattern, the exposureapparatus EX includes: the wafer holding apparatus 8 for holding thewafer W that is the exposed target; and the wafer stage WST that moveswith holding the wafer holder 54 of the wafer holding apparatus 8.Moreover, the exposure method by the exposure apparatus EX includes: thesteps 106 to 116 in which the wafer holding apparatus 8 holds the waferW; and the step 118 in which the held wafer W moves to an exposureposition.

According to the exposure apparatus EX or the exposure method in thepresent embodiment, the high throughput can be achieved by using thelarge wafer W, for example, and it is possible to stably support thewafer W when the wafer W is carried from the wafer carriage robot WLD tothe wafer holder 54 and it is possible to maintain the high flatness ofthe wafer W when the wafer W is placed on the wafer holder 54. Thus, thehigh exposure accuracy can be achieved.

Incidentally, the above described embodiment can be modified asdescribed below. Incidentally, when the following modifications areexplained, a part in FIG. 9 to FIG. 10E that corresponds to the part inFIG. 4A to FIG. 5B has a same or similar reference number and itsdetailed explanation will be omitted.

Firstly, in the above described embodiment, the wafer holding apparatus8 has three lift pins 44, for example. On the other hands, asillustrated by a wafer holding apparatus 8A in the modified example inFIG. 9, the lift pin 44 may be placed at the center of the region of thewafer holder 54 surrounded by the side wall 54 c and the plurality of(for example, six) lift pins 44 may be placed at equal angle intervalsalong the circumference CT surrounding the center, and the wafer W maybe carried by the plurality of lift pins 44.

In this modified example, for example, a Z position of the tip of thelift pin 44 at the center may be slightly lower than Z positions of thetips of the plurality of lift pins 44 surrounding it, and the wafer Wmay be carried to the wafer holder 54 by lifting down these lift pins 44under the condition where the wafer W is sucked to be convex toward aside of the wafer holder 54. According to this, even if the wafer W isthe wafer having the diameter of 450 mm, it is possible to certainlyprevent the occurrence of the wrinkle or the like when the wafer W isplaced on the wafer holder 54. Moreover, a bar-shaped member that ismovable in the Z direction without the suction unit may be used insteadof the lift pin 44 at the center. Moreover, in the above describedembodiment, the convex parts 46 c having the truncated conical shapesare placed inside the wall part 46 b of the tip part 46. On the otherhand, as illustrated by a lift pin 44C in the modified example in FIG.10A, a plurality of convex parts 46 e 1 and 46 e 2 having curvedwall-like shapes (or circular arc shapes) may be placed in the suctionregion 46 s surrounded by the wall part 46 b of the tip part 46 tosurround the suction hole 45 and the wafer W may be supported by theirupper surfaces (end parts). FIG. 10B is a vertical cross-sectional viewof the lift pin 44C in FIG. 10A. As illustrated in FIG. 10B, the axispart 45 of the lift pin 44C has, at a position that is closed to the tippart 46, an elastic hinge part 45 b that is configured to elasticallyincline and at which the diameter is smaller. Moreover, the uppersurfaces of the convex parts 46 e 1 and 46 e 1 and the upper surface ofthe wall part 46 b contact with same plane Q1, however, the height ofthe upper surface of the wall part 46 b may be slightly lower.

Even when the lift pin 44C in the modified example, the convex parts 46e 1 and 46 e 2 is capable of preventing the local deformation of thewafer W. Moreover, since the elastic hinge part 45 b is placed, the tippart 46 is capable of easily inclining (is allowed to incline) by theelastic deformation in accordance with the wafer W when the wafer Wdeforms due to its own weight. Thus, the local deformation of the waferW can be reduced more in some cases.

Moreover, as illustrated by a lift pin 44D in another modified examplein FIG. 10C, a plurality of (or one may be possible) ring-like convexparts 46 f 1 and 46 f 2 may be placed concentrically in the region ofthe tip part 46 surrounded by the wall part 46 b to surround the suctionhole 45 a. FIG. 10D is a vertical cross-sectional view of the lift pin44D in FIG. 10C. As illustrated in FIG. 10D, an opening 46 g 1 thatcommunicates with the suction hole 45 a is formed at a region of the tippart 46 of the lift pin 44D between the convex parts 46 f 1 and 46 f 2,and an opening 46 g 2 that communicates with the suction hole 45 a isformed between the convex part 46 f 2 and the wall part 46 b. Accordingto this, the air can be simultaneously and appropriately exhausted froma space between the wall part 46 b and the convex part 46 f 2, a spacebetween the convex parts 46 f 1 and 46 f 2 and a space inside the convexpart 46 f 1 when the wafer W is placed on the tip part 46, and thus thewafer W can be stably sucked. In addition, the convex parts 46 f 1 and46 f 2 is capable of preventing the local deformation of the wafer W.

Moreover, as illustrated by a lift pin 64 in additional another modifiedexample in FIG. 10E, a tip part 65 having branch toward three direction,for example, may be coupled to the upper end of the axis part 45, thewall part 65 b may be placed to surround an outline of the tip part 65,and a plurality of convex parts 65 c may be placed in the region(suction region) surrounded by the wall part 65 b to surround thesuction hole 45 a. Even when this lift pin 64 is used, the wafer W canbe lifted up and down without locally deforming the wafer W.

Moreover, as illustrated by a lift pin 44C1 in the modified example inFIG. 11A, a plurality of convex parts 46 e 1 and 46 e 2 having curvedwall-like shapes, for example, may be placed in the region of the tippart 46 surrounded by the wall part 46 b to surround the suction hole 45a, and at least one portion of the wall-like convex parts 46 e 1 and 46e 2 may be a convex part 46 e 3 having one end coupled to the wall part46 b.

Moreover, as illustrated by a lift pin 44C2 in another modified examplein FIG. 11B, a plurality of wall-like convex parts 46 e 4 may beradially placed in the region of the tip part 46 surrounded by the wallpart 46 b to surround the suction hole 45 a. In an example in FIG. 11B,end parts of the wall-like convex parts 46 e 4 are coupled to the wallpart 46 b, however, the end part of the convex part 46 e 4 may be placedto be away from the wall part 46 b. In the lift pin 44C2, the wall part46 b is formed to have a rimmed shape (ring-like shape) while theplurality of convex parts 46 e 4 are placed radially.

Moreover, as illustrated by a lift pin 44C3 in another modified examplein FIG. 11C, the plurality of convex parts 46 c having the truncatedconical shapes may be placed in the region of the tip part 46 surroundedby the wall part 46 b, and a plurality of convex parts 46 c 1 may beplaced to be coupled to the wall part 46 b and the shape of the half ofthe convex part 46 c 1 is the truncated conical shapes. According tothis, the plurality of convex parts 46 c and 46 c 1 can be placed at allgrid points of the two-dimensional grid having a regular grid in theregion of the lift pin 44C3 surrounded by the wall part 46 b.

Even when the lift pins 44C1 to 44C3 in these modified examples areused, the wafer W can be lifted up and down without locally deformingthe wafer W

Incidentally, in the lift pins 44, 44A, 44B, 64, 44C3 and the like, acylindrical or prismatic (for example, a hexagonal prismatic) convexpart having a cross-sectional area larger than an area of the uppersurface of the convex parts 46 c may be placed instead of the convexpart 46 c having the truncated conical shape or the truncated conicalshape with steps. Moreover, the convex part 46 c may be formed to have atube-like shape (for example, a circular tube-like shape or a polygonaltube-like shape) instead of the cylindrical shape or the prismaticshape.

Moreover, in the above described embodiment, the suction unit 52 holdsthe wafer W by the vacuum suction at the wafer holder 54 via the suctionholes 55A to 55D and the like, however, the wafer W may be held at thewafer holder 54 by electrostatic attraction. If the electrostaticattraction is performed, the placement surface of the wafer holder 54may be planar without placing the plurality of protruding parts 54 b onthe upper surface of the wafer holder 54 and the planar surface maysupport the wafer W.

Second Embodiment

A second embodiment will be explained with reference to FIG. 12A andFIG. 12B. A basic structure of an exposure apparatus in the presentembodiment is same as that of the exposure apparatus EX in FIG. 1. Astructure of a wafer holding apparatus is also same as that in the abovedescribed embodiment, however, a structure of the lift pin is different.Incidentally, a part in FIG. 12A and FIG. 12B that corresponds to thepart in FIG. 5A and FIG. 5B has a same or similar reference number andits detailed explanation will be omitted.

FIG. 12A is an enlarged plan view illustrating a lift pin 44E in thepresent embodiment that is configured to suck and support the wafer W.FIG. 12B is a vertical cross-sectional view illustrating the lift pin44E in FIG. 12A from which one portion of the axis part 45 is omitted.In FIG. 12A and FIG. 12B, the lift pin 44E (supporting member) includes:the axis part 45 (bar-shaped member) in which the suction hole 45 a isformed; and a tip part 46A that is coupled to the tip of the axis part45 to support the wafer W. And, the tip part 46A includes: a bottom part46Aa; a circular wall-part 46Ab that is placed at a periphery of thebottom part 46Aa; a contacting part (facing part) 48 that is fixed in aregion surrounded by the wall part 46Ab, that is made of a breathableporous member and that is configured to face the wafer W, and thecontacting part 48 communicates with the suction hole 45 a (the firstopening) in the axis part 45. The wall part 46Ab is formed to have anouter shape that is larger than the outer shape of the axis part 45.Moreover, a porous ceramic can be used as the contacting part 48, forexample. An upper surfaces of the wall part 46Ab and the contacting part48 are processed to have high flatness.

The outer shape of the wall part 46Ab of the tip part 46A is preferablya circular shape having a diameter of 5 mm to 15 mm, width (thickness)of the wall part 46Ab is preferably 0.05 mm to 0.6 mm, as one example.Incidentally, the outer shape of a convex part 46Ac may be a polygonalshape or the like. Moreover, the upper surface of the contacting part 48and the upper surface of the wall part 46Ab are at the same height (onsame plane Q1). Another structure is same as that in FIG. 4A and FIG.4B.

And, when the lift pin 44E in the present embodiment is used instead ofthe lift pin 44 in FIG. 4A, the wafer holding apparatus in the presentembodiment (a substrate holding apparatus) for holding the wafer Wincludes: the wafer holder 54 (a substrate holding part) on which thewafer W is placed; and a lift pin 44E (a supporting member) that isconfigured to be lifted up and down with respect to the wafer holder 54.And, the tip part 46A (an end part) of the lift pin 44E includes: thecontacting part 48 made of the porous member that includes a space partand that allows a pressure of at least one portion of the space part tobe a negative pressure to suck the rear surface of the wafer; and thewall part 46Ab that is formed to surround entire circumference (or atleast one portion) of the contacting part 48.

According to the present embodiment, when the wafer W is supported bythe tip part 46A of the lift pin 44E, the wafer W can be sucked bysucking the air by the suction unit 52 in FIG. 4B, for example, via thecontacting part 48 (the porous member) in the tip part 46A. Moreover, itis possible to prevent the local deformation of the wafer W at the tippart 46A, because a front surface of the contacting part 48 in theregion of the tip part 46A surrounded by the wall part 46Ab is planar.Thus, even if the wafer W is large (for example, the wafer having thediameter of 450 mm), it is possible to stably support the wafer W byenlarging the tip part 46A of the lift pin 44E and it is possible tosuppress the local deterioration of the flatness of the wafer W when thewafer W is placed at the placement surface 54 a (the target position) ofthe wafer holder 54 in FIG. 4B.

Incidentally, in the present embodiment, a height of the wall part 46Abof the lift pin 44E may be lower by 50 nm to several micrometer, forexample, than a height of the contacting part 48. If the height of thewall part 46Ab may be lower than that of the contacting part 48, the airflows through a gap between the wall part 46Ab and the wafer W when thesuction hole 45 a sucks the air and thus the wafer W can be stablysucked by Bernoulli effect in some cases.

Moreover, even in the present embodiment, a film (for example, theDiamond Like Carbon film) that allows easy slip may be formed on asurface (facing surface) of the tip part 46A that contacts with thewafer W and that is made of the silicon carbide ceramic, for example.

Moreover, an elastic hinge part may be placed at the axis part 45 of thelift pin 44E and the tip part 46A may be configured to elasticallydeform in accordance with the wafer W.

By the way, for example, in an apparatus that does not require a highaccuracy of the position of the wafer W in a direction along the XYplane, it may be assumed that the wafer is placed on the holding partand is not sucked. In this case, if a space or the like that does notsupport the wafer is under the wafer, it may be assumed that the waferdeforms by its own weight at this position and the flatness of the waferlocally deteriorates. Thus, in this case, in an apparatus that includesthe holding part on which the wafer is placed: and the supporting memberthat is configured to be lifted up and down with respect to the holdingpart, a ring-like first supporting part that supports the rear surfaceof the wafer and a second supporting part that supports the rear surfaceof the wafer in a region surrounded by the first supporting part may beplaced at an end part of the supporting member. According to this, it ispossible to prevent the local deterioration of the flatness of the waferW.

Moreover, the wafer W is circular shape having the diameter of 300 mm to450 mm in the above described embodiment, however, the diameter of thewafer W may be any value, and the diameter of the wafer W may be smallerthan 300 mm or larger than 450 mm.

Moreover, when an electronic device (or a micro device) such as asemiconductor device or the like is manufactured by using the exposureapparatus EX or the exposure method in the above described eachembodiment, the electronic device is manufactured through a step 221 atwhich function and performance of the electronic device is designed, astep 222 at which the mask (the reticle) based on the step for thedesign is manufactured, a step 223 at which the substrate (the wafer)that is the base material of the device is manufactured and it is coatedwith the resist, a substrate processing step 224 including a process ofexposing the substrate (the photosensitive substrate) with the patternof the reticle by using the exposure apparatus (the exposure method) inthe above described embodiment, a process of developing the exposedsubstrate, a process of heating (curing) and etching the developedsubstrate and the like, a device assembling step 225 (including aprocess such as a dicing process, a bonding process, a packaging processand the like), an inspection step 226 and the like.

In other words, a method of manufacturing the device includes forming apattern of a photosensitive layer on the substrate by using the exposureapparatus EX or the exposure method in the above described embodiment;and processing (developing or the like) the substrate on which thepattern is formed. At this time, according to the exposure apparatus EXor the exposure method in the above described embodiment, since thesubstrate can be held on the wafer stage with high flatness even if thesubstrate is large, it is possible to improve the throughput inmanufacturing the electronic device and it is possible to manufacturethe electronic device with high accuracy while maintaining high accuracyof the exposure.

Incidentally, the present invention can be employed not only for theabove described scan-exposure type of projection exposure apparatus (thescanner) but also for a step-and-repeat type of projection exposureapparatus (a stepper or the like). Furthermore, the present inventioncan be also employed for a dry-exposure type of exposure apparatus otherthan the liquid immersion type of exposure apparatus.

Moreover, the present invention is not limited to the exposure apparatusfor manufacturing the semiconductor device, and can be widely employedfor an exposure apparatus for a display apparatus such as a liquidcrystal element that is formed on a square glass plate, a plasma displayor the like and an exposure apparatus for manufacturing various devicessuch as an imaging element (CCD or the like), a micro machine, a thinfilm magnetic head, a DNA chip and the like, for example. Furthermore,the present invention can be employed for an exposure apparatus when amask (a photomask, a reticle or the like) on which mask pattern forvarious devices is formed is manufactured by using photolithographyprocess.

Incidentally, the present invention is not limited to the abovedescribed embodiments, and various constitutions can be employed withoutdeparting from the essence of the present invention.

DESCRIPTION OF REFERENCE CODES

-   EX1 exposure apparatus-   R reticle-   W wafer-   WST wafer stage-   8, 8A wafer holding apparatus-   44 to 44E lift pin-   45 axis part-   45 a suction hole-   46 tip part-   46 b wall part-   46 c convex part-   52 suction unit-   54 wafer holder-   56 driving unit-   62 vacuum pump

1. A substrate holding apparatus for holding a substrate, comprising: asubstrate holding part on which the substrate is placed; and asupporting member that is configured to be lifted up and down withrespect to the substrate holding part, an end part of the supportingmember including: a suction part that forms a suction region for suckinga rear surface of the substrate; and a supporting part that supports therear surface of the substrate in the suction region.
 2. The substrateholding apparatus according to claim 1, wherein the suction partincludes a wall part that surrounds the supporting part.
 3. Thesubstrate holding apparatus according to claim 1, wherein a plurality ofsupporting parts are placed in the suction region.
 4. The substrateholding apparatus according to claim 2, wherein the wall part is formedto have a rimmed shape.
 5. The substrate holding apparatus according toclaim 2, wherein the suction part includes a bottom part that is formedbelow an upper end of the wall part in a lift direction of thesupporting member, the supporting part is placed at the bottom part. 6.The substrate holding apparatus according to claim 5, wherein the upperend of the wall part is below an upper end of the supporting part by 50nm to several micrometer.
 7. The substrate holding apparatus accordingto claim 1, wherein an upper end of the supporting part is formed tohave a circular shape.
 8. The substrate holding apparatus according toclaim 1, wherein the suction part includes: a wall part that surroundsthe supporting part; and a bottom part that is formed below an upper endof the wall part in a lift direction of the supporting member, an outershape of the wall part is a circular shape having a diameter of 5 mm to15 mm and width of the wall part is 0.05 mm to 0.6 mm, a shape of anupper end of the supporting part is a circular shape having a diameterof 0.05 mm to 0.6 mm, the supporting member includes a bar-shaped partthat is coupled to the bottom part, a cross-sectional area of thebar-shaped part along a surface that intersects a direction along thelift direction is smaller than a cross-sectional area of the outer shapeof the wall part along the intersecting surface.
 9. The substrateholding apparatus according to claim 5, wherein the supporting part isformed at the bottom part to have a truncated conical shape.
 10. Thesubstrate holding apparatus according to claim 5, wherein a plurality ofsupporting parts are placed at the bottom part concentrically.
 11. Thesubstrate holding apparatus according to claim 1, wherein the supportingpart includes a wall-shaped member, a shape of an end surface of thewall-shaped member includes a curved shape.
 12. The substrate holdingapparatus according to claim 11, wherein the curved shape is a circulararc shape.
 13. The substrate holding apparatus according to claim 1,wherein the supporting part includes at least one ring-like wall-shapedmember.
 14. The substrate holding apparatus according to claim 1,wherein a plurality of supporting members are placed, the plurality ofsupporting members are placed along a circumference of a circle havingpredetermined diameter.
 15. The substrate holding apparatus according toclaim 1, wherein the substrate has a circular shape having a diameter ofapproximately 450 mm, a plurality of supporting members are placed, theplurality of supporting members are placed at the substrate holding partalong a circumference of a circle having a diameter of 180 mm to 350 mm.16. The substrate holding apparatus according to claim 1, wherein thesuction part sucks the substrate by using suction force that is causedby negative pressure.
 17. The substrate holding apparatus according toclaim 1, wherein the supporting member includes: a bar-shaped part thatis coupled to the end part; and a hinge part that allows the end part toincline with respect to the bar-shaped part in a lift direction.
 18. Thesubstrate holding apparatus according to claim 2, wherein an opening isformed at at least one portion of the suction part and the suction partincludes a bottom part that is formed below an upper end of the wallpart in a lift direction of the supporting member, a passage is formedin the supporting member, a pressure in the passage can be set tonegative pressure and the passage communicates with the opening.
 19. Thesubstrate holding apparatus according to claim 18, wherein thesupporting part is placed at the bottom part.
 20. The substrate holdingapparatus according to claim 18, wherein a plurality of supporting partsare placed in the suction region, the plurality of supporting parts areplaced around the opening concentrically.